On 13/4/2004, MaryK wrote:
>In my yard are four fruit trees (apple, I think). Unfortunately all four of
>them are caterpillar-infested. Some friends have said I need to deal w/the
>caterpillars, they'll eat all the leaves/injure or kill the tree.

Assuming that they're tent caterpillars:

Depending on how much you need the crop this year, and if the trees are
otherwise healthy, you can ignore them. A healthy tree can easily
stand being defoliated once, or even twice in a row. Remember, trees
expect to be eaten! They can cope. Tent caterpillars have boom and
bust cycles. Last year was a boom year, this year might be too, but
then they'll probably mostly go away for ten years or so. So it's
unlikely that the trees will be hit badly more than two years in a row.
Unless pesticides enter the picture--pesticides tend to keep pest
populations high, because they harm the predators more than the prey.

> I was
>going to ignore them, thinking they'd be good food for the birds. Any
>advice appreciated, am in a quandary.

The primary predators on our tent caterpillars are insects, especially
tachinid flies, with predatory wasps being a runner up. They're also
subject to at least one major virus when the populations are high like
they were last year, and might be again this year. So leaves will be
lost, but...

....they don't vanish in vain. Those voracious caterpillars eventually
turn into pupae to overwinter. And those pupae are a popular food
source for many birds and small mammals--during the winter, when food
is scarce. The adult moths are also prey for birds and bats. Without
surviving caterpillars, those other tasty entrees won't be there. The
caterpillar droppings (frass) are also great fertilizer for the trees,
and anything living under the trees (in a more natural setting, think
shrub layer and wildflowers). So those eaten leaves don't go to waste.

If you want to reduce 'pillar numbers, you can help the predators get
to them by breaking open the webs. Use a long stick, get what you can,
don't agonize over the rest. They're fun to watch, the way they form
columns getting to and from the tent, the way they sun themselves, and
all wiggle together to try to scare off predators. Keep an eye out for
white spots, which can be predator eggs.
--
Allyn Weaks allyn at tardigrade.net Seattle, WA Sunset zone 5
Pacific NW Native Wildlife Gardening: http://www.tardigrade.org/natives/
"To announce that there must be no criticism of the president, or that
we are to stand by the president, right or wrong, is not only
unpatriotic and servile, but is morally treasonable to the American
public." -- Theodore Roosevelt